Effects of processing variables on the microsegregation of directionally cast samples

Martorano, Marcelo de Aquino; Capocchi, José Deodoro Trani

doi:10.1007/s11661-000-0093-3

Cited by 20 publications

(16 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This more important role of diffusion at the surface rather than at the center of ingots has also been verified in studies of microsegregation. 28) As discussed about the present work samples, a weak trend of a decreasing amount of delta ferrite with an increasing cooling rate is observed (Fig. 3(a)).…”

Section: Effect Of Cooling Rate On the Amount Of Delta Ferritesupporting

confidence: 67%

Predicting Delta Ferrite Content in Stainless Steel Castings

2012

Self Cite

View full text Add to dashboard Cite

The distribution of delta ferrite fraction was measured with the magnetic method in specimens of different stainless steel compositions cast by the investment casting (lost wax) process. Ferrite fraction measurements published in the literature for stainless steel cast samples were added to the present work data, enabling an extensive analysis about practical methods to calculate delta ferrite fractions in stainless steel castings. Nineteen different versions of practical methods were formed using Schaeffler, DeLong, and Siewert diagrams and the nickel and chromium equivalent indexes suggested by several authors. These methods were evaluated by a detailed statistical analysis, showing that the Siewert diagram, including its equivalent indexes and iso-ferrite lines, gives the lowest relative errors between calculated and measured delta ferrite fractions. Although originally created for stainless steel welds, this diagram gives relative errors lower than those for the current ASTM standard method (800/A 800M-01), developed to predict ferrite fractions in stainless steel castings. Practical methods originated from a combination of different chromium/nickel equivalent indexes and the iso-ferrite lines from Schaeffler diagram give the lowest relative errors when compared with combinations using other iso-ferrite line diagrams. For the samples cast in the present work, an increase in cooling rate from 0.78 to 2.7 K/s caused a decrease in the delta ferrite fraction, but a statistical hypothesis test revealed that this effect is significant in only 50% of the samples that have ferrite in their microstructures.

show abstract

Section: Effect Of Cooling Rate On the Amount Of Delta Ferritesupporting

confidence: 67%

Predicting Delta Ferrite Content in Stainless Steel Castings

2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…In a recent paper, Aquino, and Trani [15] used a more refined segregation ratio proposed long ago by Poirier which gives the mean of the distance between the measurements and the nominal composition. These are the simplest parameters for comparing different samples, but much information is lost, often including hints as to the cause of the differences observed.…”

Section: Some Issues Concerning Experiments and Models For Alloy Micrmentioning

confidence: 99%

Some Issues Concerning Experiments and Models for Alloy Microsegregation

Lacaze

Benigni²,

Howe³

2003

Adv Eng Mater

View full text Add to dashboard Cite

ExperimentalFor this study, a single-grain slab of a commercial nickel base alloy was received in the as cast condition. The composition of the main alloying elements is listed in Table 1. From this slab, two bars with a diameter of about 20 mm were machined by spark erosion parallel to the direction of solidification and several pieces 15 mm in length were cut for the following heat treatments. l HT1: as cast, i.e., no heat treatment. l HT2: as cast + aged 6 h at 1080 C, i.e., 0 % solutioned and final aged. l HT3: solutioned 0,5 h at 1213 C + aged 6 h at 1080 C, i.e., partial solutioned and final aged. l HT4: solutioned 0,5 h at 1260 C + aged 6 h at 1080 C, i.e., 100 % solutioned and final aged. For microstructural investigations, the specimens were mounted, ground and polished, and finally etched by the so-called molybdenum acid. This type of reagent which attacks the c¢-phase is called negative etching. Quantitative image analysis was carried out in order to determine the c¢-volume fraction and the c¢-average size.Chemical microanalyses were carried out on a scanning electron microscope LEO 435 VP equiped with an energy dispersive spectrometer (EDS) PGT IMIX-PC. All observations and analyses were performed under 15 kV. Some X-ray maps were recorded to look for the composition of precipitates as described later. However, most of the analyses were carried out to characterize the distribution of the alloying elements at the scale of the dendritic structure. For this purpose, composition was estimated in spot mode at points located along a grid, 50 lm apart each other. Measurements have been made on 300 points for sample HT1 and 120 points in the case of sample HT4. The counting time in each point was set to 60 s for both grids. The EDS data in each point was then treated for ZAF correction using standards of pure elements, except for carbon which was not analyzed. The total species content estimated in each point, as well as the so-called ªgoodness of fitº (GOF) which characterizes the quality of the analysis, are reported on Figure 6 for each of the grids. It is first seen that the total content tends to decrease with the rank of the point analyzed. This trend is related to a continuous shift of the beam intensity during the analysis, i.e., with time. For this reason, use has been made afterwards of solute content after normalization (i.e., correction of the sum to 100 %). Concerning the quality of the analyses, it is seen that in most cases the GOF had a very low value. Counting with value higher than unity have been excluded for further analysis. Fig. 6. Correlation between silicon and manganese in the same area as Figure 3 below the peritectic temperature.

show abstract

“…These are the simplest parameters for comparing different samples, but much information is lost. Martorano and Capocchi [29] used a refined segregation ratio, and the average deviation between the measurements and nominal composition were reported.…”

Section: Literature Datamentioning

confidence: 99%

Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys

Khan

Mostafa

Aljarrah

et al. 2014

Journal of Materials

View full text Add to dashboard Cite

The effect of cooling rate on microstructure and microsegregation of three commercially important magnesium alloys was investigated using Wedge (V-shaped) castings of AZ91D, AM60B, and AE44 alloys. Thermocouples were distributed to measure the cooling rate at six different locations of the wedge casts. Solute redistribution profiles were drawn based on the chemical composition analysis obtained by EDS/WDS analysis. Microstructural and morphological features such as dendrite arm spacing and secondary phase particle size were analyzed using both optical and scanning electron microscopes. Dendritic arm spacing and secondary phase particle size showed an increasing trend with decreasing cooling rate for the three alloys. Area percentage of secondary phase particles decreased with decreasing cooling rate for AE44 alloy. The trend was different for AZ91D and AM60B alloys, for both alloys, area percentage of β-Mg17Al12 increased with decreasing cooling rate up to location 4 and then decreased slightly. The tendency for microsegregation was more severe at slower cooling rates, possibly due to prolonged back diffusion. At slower cooling rate, the minimum concentration of aluminum at the dendritic core was lower compared to faster cooled locations. The segregation deviation parameter and the partition coefficient were calculated from the experimentally obtained data.

show abstract

Effects of processing variables on the microsegregation of directionally cast samples

Cited by 20 publications

References 33 publications

Predicting Delta Ferrite Content in Stainless Steel Castings

Predicting Delta Ferrite Content in Stainless Steel Castings

Some Issues Concerning Experiments and Models for Alloy Microsegregation

Influence of Cooling Rate on Microsegregation Behavior of Magnesium Alloys

Contact Info

Product

Resources

About